What's up with healers not healing?

[Granyala]

O1n-o4n: incoming tank buster, pop cd. Wait for heals, wait for heals, wait for any type of heal, boom die to auto attacks.

Get better armor. Most tank busters are a joke.

*pops blackest night* :<

On a more serious note: this can't be very widespread behavior, since it is typically quite unhealthy for the healer to let the tank die.
I'll heal you if you drop below 50%.

[Mimilu]

On a more serious note: this can't be very widespread behavior, since it is typically quite unhealthy for the healer to let the tank die.
I'll heal you if you drop below 50%.

With 8-man content, it could be a case of one healer thinking the other healer will get it so that they both don't waste a cooldown.
With no form of voice chat, healers can't really coordinate with each other other then stopping what they're doing and typing (which can be especially bad for controller players, who will have to drop their controller to do it).
Other factors are things like the mudding and the attempted removal of proactive vs reactive healing and the lessening importance of off-tanks.